In recent years microanalysis technology in the field of liquid chromatography has been remarkably improved. Particularly super microanalysis technology, wherein a sample less than 1 .mu.l and further minute amount ranging 0.01-0.3 .mu.l is taken up as an object of analysis, has been developed as micro-high-performance LC. It has become one of the most important problems in the development of the latest LC how to pick up minute amount of a sample, precisely and in a good reproductive state, for introducing the same into a chromatographic column. In a gas chromatography (hereinafter simply called GC), which is also a representative one in parallel with the liquid chromatography in the field of chromatographic separating technology, it is a highly desirable thing to reduce the amount of the sample introduced, since the amount of the sample actually used in the separation process in the column is very small. Development of the micro amount sample introducing device is also greatly desired in this field of GC so as to make the microanalysis in GC possible.
In the conventional sample introducing devices, such as a micro-syringe which has been widely employed in LC, the disadvantages are inevitable.
(1) Since the micro-syringe determines the sample amount by the graduation impressed thereon, it is quite difficult to exactly pick up micro amount of the sample less than 1 .mu.l and to introduce it into the chromatographic system. Personal variation in the handling amount is also inevitable in this case.
(2) Thickness of a syringe needle in the micro-syringe is non-negligibly great compared to the inside diameter of the column which is less than 1 mm, and further sometimes less than 0.1 mm; so the liquid is liable to be so disturbed, while the sample is introduced and the needle is removed, as to affect the chromatogram obtained from the development of the sample.
(3) When a micro column of small inside diameter is used for analysing micro amount of the sample, it is required to minimize the dead volume above and below the column to the greatest extent for preventing the diffusion of the sample. In the introduction of the sample by a conventional syringe, as injection port is needed to be disposed at the inlet of the column, so it is extremely difficult again to reduce the dead volume here.
As the conventional sample introducing devices, sample valves such as a four-port valve, a six-port injection valve are fairy widely utilized. They are indeed useful in the introduction, while holding good reproducibility, of a sample in the amount as small as to a few micro-liters. As they have such a structure as to pick up a sample into a sample loop therein, before rotating a rotating portion of the device for connecting the sample loop to the solvent line, so that the sample may be introduced into the column, there appears an annoying problem that minimizing the inside capacity of the sample loop is impossible. From the technical stand point of view sample picking up less than 2 .mu.l, to say nothing of less than 1 .mu.l, is impossible. So they are inappropriate as a micro sample introducing device or apparatus.
With the background mentioned above the inventors of this invention proposed a novel method of introducing a sample in a micro LC and an apparatus therefor, which are described in U.S. Pat. No. 4,102,782. It discloses that even a minute amount of sample less than 1 .mu.l can be surely introduced into a column. The method and the apparatus are however still unsatisfactory in some respects such as: (1) Sample introduction operation and consequently chromatographic separation process still contains some complexity, because the sucking and delivering of the sample into the column is carried out by a pulse-motor which is forwardly and oppositely rotatable, and a mobile phase supplying line must be removed temporarily from the column so as to immerse the opening end thereof into a sample solution. And (2) the opening end of the mobile phase supplying line (a retainer tube) which has been immersed in the sample solution must be completely wiped off to remove the residue of sample stuck on the outer surface thereof. It makes the sample introduction operation considerably troublesome, and unless the wipe-off operation of the sample is enough the reproducibility of the sample will be affected.